1. Field of the Invention
The invention relates to a bioreactor, comprising                a reactor bag with a predominantly flexible bag wall which has a rigidly formed bearing area for housing a stirrer serving to circulate contents of the bag,        a shaftless stirrer, parts of which are permanently magnetic, housed inside the bag in the bearing area, and        a coil arrangement positioned outside the reactor bag with which coil arrangement a rotating magnetic field can be produced, which magnetic field interacts, in a manner exerting a torque on the stirrer, with the permanent-magnetic areas thereof.        
2. Description of the Related Art
The invention further relates to a reactor bag for a bioreactor, comprising a predominantly flexible bag wall which has a rigidly formed bearing area for housing a shaftless stirrer serving to circulate the contents of the bag, at least parts of the stirrer being permanently magnetic.
Finally, the invention relates to a stirrer to circulate the contents of a bioreactor, parts of which stirrer being permanently magnetic and comprising a plurality of paddle-like circulation elements affixed to a holder.
Such bioreactors, reactor bags and stirrers for same are known from U.S. Pat. No. 8,123,199 B2.
As is known, bioreactors serve as containers for fluids in which biological processes, such as fermentation or cell growth, are intended to take place in a controlled manner. Due to the metabolic activity of the microorganisms involved, local changes arise in the concentration of various chemical components. To maintain the same, or at least controlled, concentration conditions in the entire container, the fluid in the reactor must be stirred occasionally; preferably, in a constant manner. To avoid contamination, the stirrers are generally arranged in the interior of the otherwise closed reactor container (except for specific inlets and outlets). One difficulty is causing the stirrers located in the interior of the reactor container to move in the desired stirring direction by means of drive mechanisms usually arranged outside of the reactor container.
For bioreactors with rigid walls, such as steel tanks, a familiar solution is to affix the actual circulation elements of the stirrer, such as impellers, on a shaft that penetrates the container wall in a sealed bearing such that the stirrer shaft can simply be coupled with the drive shaft of a motor of any desired configuration.
Recently there has been a steady increase in the use of bioreactors whose actual container is designed as a flexible bag for single use. Advantages include the cost-effective manufacture of the foil bags, straightforward and space-saving storage, ease of sterilization and contamination security, as well as dispensing with the need for laborious cleaning after use. However, the problem of appropriately circulating the contents of the bag has not been definitively solved. In particular, versions with stirrer shafts that penetrate the bag wall are regarded as disadvantageous as this increases the risk of contamination, considerably increases the amount of space required for storage and, because of the necessity of providing a sealed penetration point for the shaft, renders the manufacture of the bags more complicated and expensive.
The category-defining patent U.S. Pat. No. 8,123,199 B2 discloses a shaftless stirrer having a plurality of impellers around a flat, cylindrical holder, wherein the flat, cylindrical holder is housed in a correspondingly shaped rigid vessel forming the bottom of the reactor bag. At least part of the cylindrical holder is designed to be permanently magnetic and interacts with an external magnetic field that penetrates the vessel wall. The external magnetic field is designed as a rotational field, so that the stirrer holder, along with the paddle-like circulation elements, is caused to rotate in its bearing vessel. This known device has several disadvantages. On the one hand, it is limited in that the position of the stirrer is restricted to the bottom region of the reactor bag, which can be expected to result in insufficient mixing of the reactor contents in tall bioreactors. On the other hand, the stirrer is not axially fixed in its bearing vessel—rather, to the contrary, in order to reduce bearing friction, axial raising of the stirrer by the external magnetic field is described. This means that during transport, the stirrer can easily fall out of its bearing and damage the bag walls with its sharp-edged paddles.
It is the problem of the present invention to further develop category-defining bioreactors, reactor bags and stirrers so as to overcome the disadvantages of the prior art. In particular, bioreactors and/or reactor bags with significantly reduced space requirements during storage and/or transport are to be provided. Also improved mixing of the reactor contents and safer transport and storage options are intended to result.